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What happened

Shares of Global Blood Therapeutics (GBT), a clinical-stage biotech focused on blood-based disorders, rose by 12% as of 11:45 a.m. EDT on Tuesday.

So what

The jump can be traced to the company releasing the design details of its upcoming phase 3 clinical trial for its lead compound GBT440. This drug is being studied as a potential treatment for sickle cell disease. 

This placebo-controlled study -- which is being called the HOPE study -- will enroll up to 400 patients who have sickle cell disease and have had at least one episode of vaso-occlusive crisis (VOC) in the previous year. The study's primary efficacy endpoint will be the proportion of patients who achieve a >1 g/dL increase in hemoglobin levels at 24 weeks when compared to baseline. Secondary endpoints of the study will include GBT440's ability to reduce VOC episodes and better manage symptoms of the disease when compared to placebo.

According to the Food and Drug Administration, the drug's pathway to approval would hinge on its ability to meet the study's primary endpoint and at least one secondary endpoint. Management stated that they will start screening for patients in December and that top-line data should be available by early 2019.

The markets are reacting favorably to this news as it is believed that the study's primary efficacy endpoint of increased hemoglobin levels will be an easier outcome to achieve than what the FDA has historically required of sickle cell disease drug candidates.

Now what

In June, Global Blood Therapeutics presented data from its phase 1/2 study that showed that using GBT440 led to a 1.1 g/dL increase in hemoglobin levels. Those results compared favorably to the 0.2 g/dL decrease that was observed in the placebo group. In addition, the drug was well tolerated and no serious adverse events were observed. If those results can be replicated in this larger phase 3 trial, then it appears that GBT440 will have a good chance at winning approval.

Some analysts believe that GBT440 could eventually reach peak annual sales of up to $2.7 billion, so if the company is successful, then it appears to be sitting on a gold mine.

Of course, it should be mentioned that Global Blood isn't the only company that is working to develop treatments for sickle cell disease. bluebird bio (BLUE -5.74%), another clinical-stage biotech, has a product candidate called LentiGlobin that could be a cure for sickle cell disease. While the therapy is still in phase 1/2 trials, if Bluebird ultimately succeeds at using LentiGlobin to cure patients of their disease, then it could threaten to make GBT440 obsolete. That makes Bluebird a company that Global Blood's investors will want to watch with great interest.